Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
  • A61Q19/00—Preparations for care of the skin
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K8/00—Cosmetics or similar toiletry preparations
  • A61K8/02—Cosmetics or similar toiletry preparations characterised by special physical form
  • A61K8/0241—Containing particulates characterized by their shape and/or structure
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K8/00—Cosmetics or similar toiletry preparations
  • A61K8/18—Cosmetics or similar toiletry preparations characterised by the composition
  • A61K8/19—Cosmetics or similar toiletry preparations characterised by the composition containing inorganic ingredients
  • A61K8/27—Zinc; Compounds thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G9/00—Compounds of zinc
  • C01G9/02—Oxides; Hydroxides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L11/00—Compositions of homopolymers or copolymers of chloroprene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L61/00—Compositions of condensation polymers of aldehydes or ketones; Compositions of derivatives of such polymers
  • C08L61/04—Condensation polymers of aldehydes or ketones with phenols only
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/04—Compounds of zinc
  • C09C1/043—Zinc oxide
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
  • C09J11/02—Non-macromolecular additives
  • C09J11/04—Non-macromolecular additives inorganic
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K2800/00—Properties of cosmetic compositions or active ingredients thereof or formulation aids used therein and process related aspects
  • A61K2800/40—Chemical, physico-chemical or functional or structural properties of particular ingredients
  • A61K2800/41—Particular ingredients further characterized by their size
  • A61K2800/413—Nanosized, i.e. having sizes below 100 nm
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/01—Particle morphology depicted by an image
  • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/10—Solid density

Definitions

• the present invention provides a process for preparing ball-shaped zinc oxide particles and their use.
• DE-A 199 07 704 discloses a process for the preparation of zinc oxides with a mean diameter of 5 to 30 nm and the formulation of these as concentrated dispersions in organic solvents and/or water by redispersion, wherein the dispersed zinc oxide is present substantially as isolated primary particles, i.e. agglomerate-free. Due to their fine state of division, these particles are outstandingly suitable as inorganic UV absorbers in transparent coatings or as coactivators for latex vulcanization.
• Zinc oxides prepared in this way as compared with those prepared by a calcination process, have the advantage that the primary particles are present in a non-agglomerated form or, if agglomerated to some extent, are reversibly agglomerated so they can be introduced and dispersed in gaseous, liquid or solid media in a homogeneous, primary particulate manner by means of appropriate measures.
• the primary particles grow together to give secondary particles or agglomerates with much higher particle sizes, due to the effects of heat, and these cannot be broken down into the primary particles again, either physically, mechanically or chemically, in an economic manner. Therefore the two types differ fundamentally, Which is why there are generally completely different, non-overlapping, areas of use for the two types.
• ZnO particles with spherical, ball-shaped surfaces can be obtained during preparation of the particles.
• These novel ZnO particles have improved vulcanization activity, as compared with zinc oxides which are prepared in accordance with DE-A 199 07 704 and lead to improved material properties for the vulcanizates.
• the present invention is directed to a process for the batchwise preparation of zinc oxide particles including
• R represents H or a C 1 -C 10 residue with a concentration of zinc ions (Zn) of 0.01 to 5 mol per kg of solution with
• the precipitation solution obtained after completion of the addition is matured at a temperature of 40 to 65° C. for a period of 5 to 50 min and is then cooled down to a temperature of ⁇ 25° C.
• the present invention also provides a process for the continuous preparation of zinc oxide particles including
• B2) a methanolic potassium hydroxide solution with a concentration of hydroxide ions (OH) of 1 to 10 mol per kg of solution
• the precipitation solution formed is matured at a temperature of 40 to 65° C. for a period of 5 to 50 min and is then cooled down to a temperature of ⁇ 25° C.
• the present invention provides a process for the batchwise preparation of zinc oxide particles including
• the precipitation solution obtained after completion of the addition is matured at a temperature of 40 to 65° C. for a period of 5 to 50 min and is then cooled down to a temperature of ⁇ 25° C.
• the present invention also provides a process for the continuous preparation of zinc oxide particles including
• B2) a optionally methanolic sodium hydroxide solution, which may optionally contain dissolved KOH, with a total concentration of 1 to 10 mol of hydroxide ions (OH) per kg of solution
• the precipitation solution formed is matured at a temperature of 40 to 65° C. for a period of 5 to 50 min and is then cooled down to a temperature of ⁇ 25° C.
• Zinc oxides prepared according to the present invention preferably have a mean primary particle size of 5 to 50 nm, more preferably of 5 to 20 nm.
• the particle size can be determined by ultracentrifuge measurements (H.G. Müller, Colloid. Polym. Sci., 267, 1113-1116 (1989)).
• a substantial proportion of the particles i.e. at least 60%, preferably at least 80%, more preferably at least 95% of the particles, have a spherical, ball-shaped surface, wherein the %-age data is calculated from the number of ball-shaped particles, with reference to the total number of particles found in a volume increment.
• the method used to determine this includes producing TEM images of the methanolic zinc oxide precipitates prepared in accordance with the present invention and evaluating the images visually.
• the zinc oxide precipitate or dispersion being investigated can be diluted about 1:1000 with a mixture of 2 parts by weight of ethylene glycol and 1 part by weight of water, dripped onto a TEM grid and dried.
• spherical or “ball-shaped” mean that the ratio of the particle length to the particle width is of 3:1 to 1:1, preferably 2:1 to 1:1, more preferably 1.5:1 to 1:1.
• the proportion of secondary particles is ⁇ 20 wt. %, preferably ⁇ 5 wt. %, preferably 2 wt. %, with respect to the total amount of precipitated zinc oxide.
• a 10 wt. % strength ZnO dispersion can be prepared in the same way as in working Example 6, stored for 5 days at room temperature and then filtered through a 0.2 ⁇ m cellulose membrane filter. The filter residues can be dried and weighed. The proportion of agglomerates can then be obtained by dividing the amount of solid determined in that way by the amount of ZnO used for the determination.
• Methanol/water mixtures are preferably used.
• the use of methanol with less than 1 wt. %, preferably less than 0.5 wt. % of water is preferred.
• the use of methanol-free solvent systems does not lead to the formation of zinc oxide particles within the scope of the present invention.
• [0038] used in the process according to the present invention can be obtained by simple dissolution of the commercially available zinc salt, in a methanolic solvent as described above.
• coarsely divided zinc oxide can also be initially introduced into a methanolic solvent and can be converted into a zinc salt solution by simply adding the corresponding acid and optionally water.
• the residue R in formula (I) represents preferably H or an aliphatic or cycloaliphatic residue, more preferably H, CH 3 , C 2 H 5 or C 3 H 7 .
• zinc acetate optionally in form of its dihydrate can be used as zinc salt in the process of the present invention.
• These solutions have a zinc ion concentration of preferably 1 to 2 mol per kg of solution.
• the hydroxide solutions A2) or B2) have a concentration of hydroxide ions of preferably 3 to 6 mol per kg of solution.
• a methanolic or aqueous sodium hydroxide solution which may optionally contain dissolved potassium hydroxide, can also be used instead of a methanolic potassium hydroxide solution.
• KOH-containing precipitation media KOH and NaOHIKOH-containing solutions
• KOH and NaOHIKOH-containing solutions KOH and NaOHIKOH-containing solutions
• the zinc salt solution A1) or B1) is kept at a constant temperature of 30 to 65° C., preferably 50 to 65° C., more preferably 55 to 58° C.
• the hydroxide solutions A2) or B2) have a temperature of 10 to 65° C., preferably 15 to 30° C., more preferably 18 to 25° C.
• the molar ratio of base (OH) to Zn is 1.7-1.8, more preferably 1.72-1.78.
• ratios of less than 1.7 or more than 1.8 are also possible. Even when the ratio is ⁇ 1.7, particles with the initially described sizes, shapes and properties can be obtained, but the amount of Zn which is not converted to ZnO is too large (poor space-time yield) so the process becomes unnecessarily costly and this embodiment is not preferred.
• the ratio is >1.8, preferably >1.9, precipitation can no longer be controlled in such a way that particles with the initially described shapes and properties are obtained. Therefore a ratio >1.8 may not be preferred.
• substances can also added before, during or after precipitation.
• alkoxysilanes such as tetraethyl orthosilicate, zwitterionic compounds such as “betaine” (carboxytrimethylammonium) or 6-aminohexanoic acid or surface-active substances from colloid chemistry which are known to a person skilled in the art.
• Anionic, cationic or non-ionic surfactants, emulsifiers and/or stabilizers with carboxylate, sulfonate, ammonium or polyether groups may be preferred.
• the process according to the present invention is normally performed at atmospheric pressure (1013 mbar), but may also be performed at higher or lower pressures.
• the process temperatures should then be adjusted accordingly so that they are not above the boiling point of the lowest-boiling component in the process.
• the upper limit of 65° C. for the process temperature corresponding to the boiling point of methanol at that pressure
• An upper limit of >65° C. for the temperature during the process is therefore possible.
• the energy input for the stirrers is generally 0.1 to 3 Watts per liter, preferably 0.2 to 0.8 Watts per liter.
• Solution A2) is preferably added to A1) within less than 6 minutes, preferably within less than 4 minutes, more preferably within less than 3 minutes.
• the temperature during the precipitation process is preferably, ⁇ 65° C., more preferably, ⁇ 60° C., most preferably 55 to 60° C.
• the subsequent maturation process can be performed by continuing to stir the precipitation solution at preferably 50 to 65° C., more preferably 55 to 60° C. for preferably 20 to 40 min, more preferably 30 to 35 min.
• the lower limit of 40° C. cited as the lower limit for the maturation temperature in all the process variants is the temperature above which maturation proceeds satisfactorily and above which therefore the maturation process is also normally performed. However, this does not exclude the use of maturation temperatures of ⁇ 40° C.
• Subsequent cooling down is achieved by the use of external cooling with a suitable medium such as cold water or brine, wherein the final temperature is preferably 10 to 25° C., more preferably 15 to 20° C., which means that further growth of the particles to give primary particles >50 nm, the formation of particles with e.g. rod-shaped morphology and/or agglomeration to give secondary particles, is prevented.
• the cooling process for the entire precipitation solution preferably takes less than 60 min.
• the two solutions B1) and B2) can be continuously brought together in a mixing unit of the static mixer type, or a T- or Y-junction piece, optionally with a downstream mixing section, and blended.
• the mixing units and the rates of flow of the reactant solutions or the precipitation solution are designed in such a way that homogeneous blending is achieved within preferably less than 6, preferably less than 4, more preferably less than 3 seconds.
• the amount delivered of solutions B1) and B2) is adjusted in the process according to the present invention in such a way that, with the given starting temperatures of B 1) and B2), the temperature of the precipitation solution is preferably, ⁇ 65° C., more preferably, ⁇ 60° C. and more preferably 55 to 60° C. and the criterion for mixing time given above is complied with.
• Subsequent particle maturation can be performed by passing the precipitation solution through a residence time section which is kept at a constant temperature of 50 to 65° C., preferably 55 to 60° C., wherein the latter is designed in such a way that the residence time for a volume increment of precipitation solution is preferably 20 to 40 min, more preferably 30 to 35 min.
• Subsequent cooling down to preferably 10 to 25° C., more preferably 15 to 20° C. can be performed by e.g. collecting the precipitation solution emerging from the residence time section in a tank with adequate jacket cooling or via heat exchangers from the prior art which are known per se to a person skilled in the art.
• a residence time section is not used, wherein the entire precipitation solution being produced after the blending procedure is collected in a stirred tank cooled to ⁇ 20° C., preferably, ⁇ 10° C. (effective internal temperature) and, after a desired time, this is heated with stirring to preferably 50 to 65° C., more preferably 55 to 60° C., without the further addition of any precipitation solution, and is matured for preferably 20 to 40 min, more preferably 30 to 35 min (semi-continuous process).
• Subsequent cooling down is achieved by external cooling with a suitable medium such as cold water or brine, wherein the final temperature is preferably 15 to 25° C., more preferably 15 to 20° C.
• the cooling process for the entire precipitation solution preferably takes less than 60 min.
• dissolved substances can be removed from the zinc oxide precipitates prepared and matured in accordance with the present invention and the precipitates are concentrated down by sedimentation in a centrifuge or under the effects of gravity or by cross-flow membrane filtration (nanofiltration or ultrafiltration using ceramic membranes having an average pore diameter of 5 nm build in multi-channel elements).
• From the zinc oxides or their precipitates prepared by the process according to the present invention can be prepared dispersions in a variety of organic or aqueous solvents or mixtures, optionally with the aid of mechanical or chemical dispersers such as ionic or non-ionic surfactants, and/or surface-modifying compounds such as alkanoic acids and alkanoates with preferably 3 to 25 carbon atoms such as e.g. oleic acid, amines, aminoalcohols, alkoxysilanes or the products of hydrolysis of one or more alkoxysilanes by aqueous acids.
• mechanical or chemical dispersers such as ionic or non-ionic surfactants, and/or surface-modifying compounds
• alkanoic acids and alkanoates with preferably 3 to 25 carbon atoms such as e.g. oleic acid, amines, aminoalcohols, alkoxysilanes or the products of hydrolysis of one or more alkoxysilanes by aqueous acids
• the dispersions mentioned above are prepared by stirring the methanolic zinc oxide precipitates obtainable in accordance with the present invention into organic and/or aqueous solvents or mixtures of these, optionally with the aid of surface-modifying substances.
• the methanol present in the dispersions can be removed by distillation in order to improve the dispersion status of the particles.
• water, monoalcohols, diols, aminoalcohols, alkanes, ethers, esters and also mixtures thereof can be used as solvents.
• halogenoalkanes and halogenoalkane/alcohol mixtures such as dichloromethane/methanol and chloroform/methanol mixtures, are also preferred.
• alkanoic acids and alkanoates with preferably 3 to 25 carbon atoms, such as e.g. oleic acid, amines, preferably alkyl-, dialkyl- or trialkylamines, as stabilizers enables the zinc oxide particles prepared in accordance with the present invention also to be provided as a stable finely divided dispersion in non-polar solvents such as oils, alkanes and/or aromatic compounds.
• non-polar solvents such as oils, alkanes and/or aromatic compounds.
• a zinc oxide precipitate prepared in accordance with the invention is added, with stirring, to a zinc oxide precipitate prepared in accordance with the invention and then a mixture of a monoalcohol, preferably n-butanol, and at most 5 wt. % of triethanolamine is added and after stirring for 30 minutes the methanol present is removed by distillation.
• a monoalcohol preferably n-butanol
• triethanolamine is added and after stirring for 30 minutes the methanol present is removed by distillation.
• the solids concentration of the zinc oxide precipitates used to formulate dispersions is typically 5 to 80 wt. %, preferably 15 to 40 wt. %.
• the conductivity of the methanolic phase in these precipitates is less than 200 mS/cm, preferably less than 15 mS/cm, more preferably 0.005 to 5 mS/cm.
• the present invention also provides zinc oxides obtainable by the process according to the present invention and also dispersions prepared from same.
• the use of these dispersions of primary particulate redispersed zinc oxides includes the preparation of molded items and/or coatings, for example those with UV-absorbing and/or a biocidal effect.
• Coatings are understood to be either polymeric systems for the coating of or adhesion of materials such as metals, plastics or glass or else cremes, salves, gels or similar solid or free-flowing formulations for use in the cosmetic or pharmaceutical area.
• Zinc oxides according to the present invention can also be used in plastics, rubbers, sealant compositions or adhesive compositions as fillers and/or additives with e.g. an acid-binding or catalytic effect.
• the redispersible nanoparticulate zinc oxides according to the present invention can, as mentioned, be used as vulcanization coactivators during the preparation of latices based on natural and synthetic rubbers of all kinds.
• Suitable rubbers which can be used to prepare latices include, apart from the wide variety of different natural latex formulations, synthetic rubbers such as natural latex and synthetic polyisoprenes, acrylonitrile/butadiene copolymers optionally containing carboxylated and/or self cross-linking groups, styrene/butadiene copolymers optionally containing carboxylated and/or self cross-linking groups, acrylonitrile/butadiene/styrene copolymers optionally containing carboxylated and/or self cross-linking groups, and optionally carboxylated chlorobutadiene latices.
• synthetic rubbers such as natural latex and synthetic polyisoprenes, acrylonitrile/butadiene copolymers optionally containing carboxylated and/or self cross-linking groups, styrene/butadiene copolymers optionally containing carboxylated and/or self cross-linking groups, acrylonitrile
• zinc oxide dispersions according to the invention are used in amounts of 2.0 to 0.01, preferably 0.5 to 0.05 parts by weight, with respect to 100 parts by weight of a latex mixture (dry wt./dry wt.) during vulcanization.
• the zinc oxide dispersions used have a ZnO content of typically 5 to 40 wt. %, preferably 15 to 25 wt. %, wherein any aqueous medium, preferably mixtures of ethylene glycol/water, triethanolamine/water or ethylene glycol/water/triethanolamine, are suitable as the dispersion medium.
• the ratio by weight of ethylene glycol to water is preferably 5:1 to 1:1, more preferably 2.5:1 to 1.5 1.
• the ratio by weight of triethanolamine amine to water is preferably 1:5 to 1:1, more preferably 1:2.5 to 1:1.5.
• the ratio by weight of ethylene glycol to water to triethanolamine is preferably 10:5:5 to 10:5 0.1, more preferably 10:5:2 to 10:5:0.5.
• the concentration of zinc oxide was determined in a similar way to that described in DE-A 199 07 704, by UV spectroscopic absorption measurements or, after dissolving the zinc oxide with glacial acetic acid or ammonia, by a volumetric titration with EDTA, using indicator buffer tablets.
• the actual precipitation process was initiated by transferring the major amount of the methanolic KOH solution over the course of 5 min. The temperature then rose to 58° C. After completion of the transfer process, the mixture was heated to 60° C. and the temperature was held for 35° C. Then the mixture was cooled to 20° C. by means of external water-cooling.
• the particles were compacted by sedimentation of the ZnO particles in the precipitate prepared according to example 1 for a period of 12 hours under the effects of gravity, then the clear methanolic supernatant liquid was removed from above via a lance using an attached pump, 550 g of fresh methanol were added with stirring and then the particles were allowed to settle out for a further 12 hours. The procedure was repeated a further 4 times, until the conductivity of the methanol removed from above was 1.9 mS/cm.
• the compacted zinc oxide precipitate had a ZnO content of 37.0 wt. %.
• a ZnO precipitate prepared according to example 1 was allowed to settle out for 4 hours.
• the supernatant liquid (2043 g, conductivity 24.3 mS) was removed from above and the residue was stirred for 30 min with 600 g of methanol.
• the dispersion of primary particulate redispersible particles was then centrifuged for 30 min at 5500 rpm in a laboratory centrifuge (Haraeus Variofuge RF, rotor radius 20.4 cm).
• the transparent supernatant liquid (837 g, conductivity 15.7 mS) was decanted off.
• the solid residue (263.1 g) was redispersed with 263.1 g of dichloro-methane.
• the dispersion of primary particulate redispersed ZnO particles made up had a weight of 508.3 g. After settling out for 72 h, this mixture was centrifuged for 30 min at 5500 rpm and pressure filtered through a 1 Am filter. A translucent, long-term stable dispersion of primary particulate redispersed particles was produced.
• 167 g of a natural latex of the-HA type (according to the ISO 2004 specification) was mixed, at room temperature with stirring, with 5.0 parts by weight of a 10 wt. % strength aqueous potassium hydroxide solution and with 0.70 parts by weight of a 20 wt. % strength potassium laurate solution as stabilizer. Then 20.6 parts by weight of a vulcanization paste, consisting of 1.5 parts by wt. of colloidal sulfur, 0.6 parts by wt. of zinc dithiocarbamate (ZDBC), 1.5 parts by wt. of zinc mercaptobenzothiazole (ZMBT), 1.5 parts by wt.
• ZDBC zinc dithiocarbamate
• ZMBT zinc mercaptobenzothiazole
• the solids content of this latex compound was 56 wt. %.
• the data relating to parts by wt. refer to 100 parts by weight of dry rubber substance, which corresponds to 167 parts by weight of wet natural latex.
• the results show that the zinc oxide prepared according to the present invention provides comparable strength values, despite a lower amount being used, to those obtained with the use of 2.0 parts by wt. of white sealer zinc oxide or 1.0 parts by wt. of a zinc oxide with a high surface area.
• the modulus at 300% extension is much lower when using the zinc oxide prepared according to the present invention than when using comparison samples with zinc oxides which are not according to the present invention. This effect leads to greater wearer comfort which is of importance, for example, when producing latex gloves.
• the extension up to the break point in the case of trial series 10-A according to the invention also gives higher values than the comparison tests 10-B and 10-C.
• 167 g of a natural latex of the HA type (according to the ISO 2004 specification) were mixed with 5.0 parts by wt. of a 10 wt. % strength aqueous potassium hydroxide solution and with 1.25 parts by weight of a 20 wt. % strength potassium laurate solution as stabilizer, at room temperature and with stirring. Then 7.8 parts by weight of a vulcanization paste consisting of 1.0 parts by wt. of colloidal sulfur, 0.6 parts by wt. of zinc dithiocarbamate (ZDBC), 0.3 parts by weight of zinc mercaptobenzothiazole (ZMBT), 1.0 parts by wt.
• ZDBC zinc dithiocarbamate
• ZMBT zinc mercaptobenzothiazole
• 11-A 0.05 parts by wt. of a zinc oxide prepared according to example 6 and
• 11-B 0.05 parts by wt. of a zinc oxide prepared according to DE-A 199 07 704
• 11-C 1.0 parts by wt. of zinc oxide WS (surface area 10 m 2 /g, manufactured by Grillo Zinkoxid GmbH, Germany; powdered form), used as a 50 wt. % strength aqueous paste
• 11-D 0.5 parts by wt. of active zinc oxide (surface area at least 45 m 2 /g;
• nanoparticulate zinc oxide according to example 6, according to the invention exhibits a higher strength, a lower modulus and a higher extension at break in comparison to the nanoparticulate zinc oxide already described but also as compared with the types of zinc oxide used in practice.

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